Just one between Z wave and zigbee?
For many of us, myself included, the primary reason for selecting SmartThings was that it supports multiple protocols. I like to choose the protocol based on the specific device placement and use. So at my house, we typically use Lutron Caseta (which is neither zigbee nor zwave) for light switches, zigbee for smart bulbs and sensors, and Zwave for door locks, plug-in pocket sockets, and in wall micros. We also have some Bluetooth devices which are used with HomeKit.
If I had to pick just one, personally I wouldn’t give up the hue bridge, and I really like zigbee sensors, so it would be zigbee, but I know that I might have some issues with Wi-Fi interference with fixed location devices like door locks. I have a pretty good technical background and know how to deal with that stuff, but it can be challenging for people who don’t have a strong technical background and access to the right tools. But that setup would mean giving up my Lutron light switches, which I really don’t want to do.
If I were recommending a single protocol solution for someone who didn’t have a strong technical background and just had a regular house in the US and was going to install everything themselves, I would recommend Z wave. It’s just a little simpler for DIY Single protocol installations.
But in the real world people are not usually limited to just one protocol, so for someone with simple needs who is doing everything themselves and didn’t have a strong technical background, these days I more commonly suggest they look at HomeKit with Lutron switches and the Phillips hue bridge not just for smart bulbs but also for their sensors and handheld remotes. If they want something pretty simple that works with SmartThings, it’s the same suggestions but they can also use zwave locks and button devices and zigbee sensors if they want.
So that’s the answer I would give, but in the real world I just don’t stick to only one protocol, either for myself or when making recommendations to others. Choice is good. 